Background
With the development of micro-nano electronics and photoelectron technology, the application of optical communication networks and optical sensing systems to magneto-optical functional devices is increasingly urgent. Magneto-optical isolators and magneto-Optical Current Sensors (MOCTs) are the most typical devices. The magneto-optical isolator is also called as an optical diode, and the nonreciprocal property of the magneto-optical isolator breaks the time reversal symmetry of light propagation, can ensure the unidirectional transmission of light waves in a light path where the magneto-optical isolator is positioned, avoids the instability generated by the influence of reflected light on a laser light source, and is an indispensable device in an optical communication network and on an optical information processing chip. The MOCT measures the current intensity by testing the magnetic field intensity generated by the current, and has significant advantages over the conventional current transformer in the aspects of linearity, safety and the like, thereby playing an increasingly important role in power measurement, particularly in current measurement of high-voltage transmission lines.
The integration and manufacture of magneto-optical devices on optical waveguide chips are not concerned before facing the application requirements of optical information processing and optical sensing. Until now, the technology for manufacturing magneto-optical devices (such as magneto-optical isolators and MOCTs) constructed by tiny optical elements and optical fiber elements has been developed to a great extent and successfully applied to optical sensing and optical communication networks. However, these magneto-optical devices based on discrete components have disadvantages of large size and high manufacturing cost, on the one hand, and on the other hand, the discrete devices cannot be applied to integrated optical information processing chips. Driven by the requirement of device function integration, the fabrication of integrated magneto-optical devices has become a leading direction for researchers. The integration of the magneto-optical device is not only embodied in the great reduction of the size of the device, but also in the great reduction of the device cost brought by mass production, and is further embodied in the convenience brought to the optical information processing chip by function integration.
The magneto-optical waveguide is a basic structural unit for constructing an integrated magneto-optical device, and the development of the high-performance magneto-optical waveguide has fundamental significance for realizing the magneto-optical device.
Silicon-based SOI waveguides are considered an important development direction in the optoelectronics industry because they have superior performance and are compatible with CMOS processes. The integration of the magneto-optical function in the silicon-based integrated optical chip is pulled by the requirements of the magneto-optical isolator and the application of various sensors based on the magnetic field sensing principle, and becomes an emerging research hotspot. The magneto-optical waveguide is a foundation for building magneto-optical function integration and is a core problem which needs to be solved for realizing the magneto-optical function integration.
The fabrication of magneto-optical waveguides on silicon substrates is currently achieved by means of heterogeneous integration. The cross-sectional structure of such an optical waveguide is shown in fig. 1. Namely, the Ce-doped YIG crystal 4 (magneto-optical material) is bonded with the SOI wafer, the Ce-doped YIG crystal 4, the ridge top layer silicon core part 3 and the silicon oxide layer 2 form a composite magneto-optical waveguide, and the ridge optical waveguide core part formed by the ridge top layer silicon core part 3 realizes the magneto-optical nonreciprocal phase shift function. However, this technical approach faces two challenges: firstly, the mismatch degree between the optical parameters of the Ce-doped YIG crystal 4 and the optical parameters of the ridge top silicon core 3 serving as the ridge optical waveguide core is large, so that large nonreciprocal phase shift is difficult to obtain; secondly, the compatibility of the manufacturing technology of the magneto-optical waveguide and the CMOS process is poor, and the large-scale popularization of the technology is limited by the technical difficulty and reliability of the combination between the Ce-doped YIG crystal 4 and the ridge-shaped top layer silicon core 3 in the SOI substrate.
Disclosure of Invention
The invention aims to provide a silicon-based magneto-optical nonreciprocal ridge optical waveguide.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention forms the core of the strip-shaped optical wave on the basis of the top silicon on the SOI wafer. This optical waveguide is characterized in that: the core of the rib optical waveguide comprises two parts, one part is a ferromagnetic metal nanoparticle doped strip-shaped top silicon core 5 located at the uppermost layer of the waveguide core and the other part is a rib-shaped top silicon core 3 located between the ferromagnetic metal nanoparticle doped strip-shaped top silicon core 5 and the silicon oxide layer 2, wherein the ferromagnetic metal nanoparticles in the ferromagnetic metal nanoparticle doped strip-shaped top silicon core 5 are formed in situ in the top silicon on the SOI substrate using a doping technique.
The ferromagnetic metal material is Fe, Co or Ni.
The invention has the beneficial effects that:
the ferromagnetic metal nano-particle doped strip-shaped top layer silicon core part 5 is used as a magneto-optical functional layer and has higher magneto-optical activity than the Ce-doped YIG crystal 4, so that the size of the device can be greatly reduced, and the manufacturing of the silicon-based magneto-optical nonreciprocal ridge optical waveguide can be realized. Furthermore, the ferromagnetic metal nanoparticles in the ferromagnetic metal nanoparticle doped strip-shaped top silicon core 5 in the SOI optical waveguide containing the ferromagnetic metal nanoparticles are formed in situ in the top silicon on the SOI substrate by a doping technology, the problem of matching between the optical parameters of the magneto-optical material and the optical parameters of the SOI ridge-shaped top silicon core 3 is solved, and the problem of compatibility between the magneto-optical material and the silicon-based optical waveguide manufacturing process is solved.
The preparation of the silicon-based SOI optical waveguide containing the ferromagnetic metal nanoparticles can be realized by a conventional CMOS compatible process, and has the advantages of the existing silicon-based optical waveguide process.
Detailed Description
The invention is further illustrated by the following figures and examples.
As shown in fig. 2, the silicon-based magneto-optical nonreciprocal optical waveguide is fabricated on an SOI substrate. A silicon oxide layer 2 is arranged above a substrate silicon 1 of the SOI substrate; a ridge-shaped top silicon core part 3 is arranged above the silicon oxide layer 2; a ferromagnetic metal nanoparticle doped strip-shaped top silicon core part 5 is arranged above the ridge-shaped top silicon core part 3; ferromagnetic metal nanoparticles doped in the strip-shaped top silicon core 5 are formed in situ in the top silicon on the SOI substrate by a doping technique; the rib-shaped top layer silicon core part 3 and the ferromagnetic metal nano-particle doped strip-shaped top layer silicon core part 5 jointly form a silicon-based rib-shaped optical waveguide core part. The silicon-based ridge optical waveguide has the characteristics of magneto-optical nonreciprocal optical waveguide.
The ferromagnetic metal in the ferromagnetic metal nanoparticle doped strip-shaped top silicon core 5 is Fe, Co or Ni.
The manufacturing steps of the invention are as follows:
step A) doping the ferromagnetic metal nanoparticles on the surface layer of the flat top silicon 6 (step A in figure 3).
Firstly, preparing the upper layer of the flat-plate-shaped top layer silicon 6 on the SOI substrate into flat-plate-shaped ferromagnetic metal nano particle doped top layer silicon 7 through ion implantation and subsequent annealing process on the surface of the SOI substrate; the process parameters of ion implantation are controlled, and the thickness of the top silicon 7 doped with the flat ferromagnetic metal nanoparticles can be controlled, so that the flat top silicon 6 is partially doped in the thickness direction, namely the thickness of the doped flat top silicon 6 is greater than zero.
Step B) processing of the ridge optical waveguide (step B in fig. 3).
Adopting the conventional silicon-based ridge optical waveguide manufacturing technology to manufacture a ridge optical waveguide on the basis of doping the top layer silicon 7 and the flat top layer silicon 6 with the flat ferromagnetic metal nanoparticles above the silicon oxide layer 2 of the SOI substrate, and forming a ferromagnetic metal nanoparticle doped strip-shaped top layer silicon core part 5 by doping the top layer silicon 7 with the flat ferromagnetic metal nanoparticles after the manufacture is finished; the flat plate-like top layer silicon 6 forms a ridge-like top layer silicon core portion 3. The ferromagnetic metal nanoparticles doped strip-shaped top silicon core 5 and the ridged top silicon core 3 together form the core of the ridged optical waveguide.
Example 1
The following takes a silicon-based magneto-optical nonreciprocal ridge optical waveguide doped with Fe metal nanoparticles as an example to describe the manufacturing method of the optical waveguide, as shown in fig. 3:
(A) doping ferromagnetic metal nanoparticles on the surface layer of the flat top silicon 6 on the SOI substrate (step A in FIG. 3):
using ion implantation equipment, SOI is used as substrate (the thickness of the flat top layer silicon 6 in SOI substrate is 220nm, as shown in the upper diagram of FIG. 3), ion implantation is performed at room temperature, Fe ions are accelerated to 45keV, and the implantation dosage is (1-10) × 1017ion/cm2(ii) a And after the ion implantation is finished, annealing the SOI substrate at 800-1200 ℃, wherein the annealing time is 2-8 h. Through the ion implantation and annealing processes, Fe nanoparticles are formed in the thickness range of about 20-40 nm at the upper part of the tabular top layer silicon 6 in the SOI substrate, and the upper part of the tabular top layer silicon 6 is converted into tabular ferromagnetic metal nanoparticle doped top layer silicon 7 (as shown in the figure 3).
(B) Manufacturing a ridge optical waveguide on the surface of the SOI substrate by adopting a micro-machining process (as shown in a step B of figure 3):
adopting the conventional silicon-based ridge optical waveguide manufacturing technology to manufacture a ridge optical waveguide on the basis of doping the top layer silicon 7 and the flat top layer silicon 6 with the flat ferromagnetic metal nanoparticles above the silicon oxide layer 2 of the SOI substrate, and forming a ferromagnetic metal nanoparticle doped strip-shaped top layer silicon core part 5 by doping the top layer silicon 7 with the flat ferromagnetic metal nanoparticles after the manufacture is finished; the flat plate-like top layer silicon 6 forms a ridge-like top layer silicon core portion 3. The ferromagnetic metal nanoparticle doped strip top silicon core 5 and the rib top silicon core 3 together form the core of a rib optical waveguide (as shown in the lower graph of fig. 3). The cross-sectional shape and structural details of the ridge waveguide are shown in fig. 4: w is 6000nm, H1 is 20-40 nm, H3 is 60-80 nm, and H3 is 120 nm.
Example 2
The following takes a Co metal nanoparticle doped silicon-based magneto-optical nonreciprocal ridge optical waveguide as an example, and introduces the manufacturing method of the optical waveguide, as shown in fig. 3:
(A) doping ferromagnetic metal nanoparticles on the surface layer of the flat top silicon 6 on the SOI substrate (step A in FIG. 3):
using ion implantation equipment, using SOI as substrate (the thickness of the flat top layer silicon 6 in the SOI substrate is 220nm, as shown in the upper diagram of FIG. 3), performing ion implantation at 500 deg.C, accelerating Co ions to 0.4-2.5 MeV, and implanting dosage (1-10). times.10)12ion/cm2(ii) a And after the ion implantation is finished, annealing the SOI substrate at 800-1200 ℃, wherein the annealing time is 0.5-3 h. Through the ion implantation and annealing processes, Co nanoparticles are formed in the thickness range of about 20 to 40nm at the upper portion of the top silicon 6 in the form of a flat plate in the SOI substrate, and the upper portion of the top silicon 6 in the form of a flat plate is converted into top silicon 7 doped with ferromagnetic metal nanoparticles (as shown in fig. 3).
(B) Manufacturing a ridge optical waveguide on the surface of the SOI substrate by adopting a micro-machining process (as shown in a step B of figure 3):
adopting the conventional silicon-based ridge optical waveguide manufacturing technology to manufacture a ridge optical waveguide on the basis of doping the top layer silicon 7 and the flat top layer silicon 6 with the flat ferromagnetic metal nanoparticles above the silicon oxide layer 2 of the SOI substrate, and forming a ferromagnetic metal nanoparticle doped strip-shaped top layer silicon core part 5 by doping the top layer silicon 7 with the flat ferromagnetic metal nanoparticles after the manufacture is finished; the flat plate-like top layer silicon 6 forms a ridge-like top layer silicon core portion 3. The ferromagnetic metal nanoparticle doped strip top silicon core 5 and the rib top silicon core 3 together form the core of a rib optical waveguide (as shown in the lower graph of fig. 3). The cross-sectional shape and structural details of the ridge waveguide are shown in fig. 4: w is 6000nm, H1 is 20-40 nm, H3 is 60-80 nm, and H3 is 120 nm.
Example 3
The following takes a silicon-based magneto-optical nonreciprocal ridge optical waveguide doped with Ni metal nanoparticles as an example to describe the manufacturing method of the optical waveguide, as shown in fig. 3:
(A) doping ferromagnetic metal nanoparticles on the surface layer of the flat top silicon 6 on the SOI substrate (step A in FIG. 3):
using ion implantation equipment, using SOI as substrate (the thickness of the flat top layer silicon 6 in the SOI substrate is 220nm, as shown in the upper diagram of fig. 3), performing ion implantation at 350-400 deg.C, accelerating Ni ions to 0.4-0.5 MeV, and implanting dosage (1-10) × 1017ion/cm2(ii) a And after the ion implantation is finished, annealing the SOI substrate at 400-1000 ℃ for 0.5-4 h. Through the ion implantation and annealing processes, Ni nanoparticles are formed in the thickness range of about 20 to 40nm at the upper portion of the plate-shaped top silicon 6 in the SOI substrate, and the upper portion of the plate-shaped top silicon 6 is converted into a plate-shaped ferromagnetic metal nanoparticle-doped top silicon 7 (as shown in the diagram of fig. 3).
(B) Manufacturing a ridge optical waveguide on the surface of the SOI substrate by adopting a micro-machining process (as shown in a step B of figure 3):
adopting the conventional silicon-based ridge optical waveguide manufacturing technology to manufacture a ridge optical waveguide on the basis of doping the top layer silicon 7 and the flat top layer silicon 6 with the flat ferromagnetic metal nanoparticles above the silicon oxide layer 2 of the SOI substrate, and forming a ferromagnetic metal nanoparticle doped strip-shaped top layer silicon core part 5 by doping the top layer silicon 7 with the flat ferromagnetic metal nanoparticles after the manufacture is finished; the flat plate-like top layer silicon 6 forms a ridge-like top layer silicon core portion 3. The ferromagnetic metal nanoparticle doped strip top silicon core 5 and the rib top silicon core 3 together form the core of a rib optical waveguide (as shown in the lower graph of fig. 3). The cross-sectional shape and structural details of the ridge waveguide are shown in fig. 4: w is 6000nm, H1 is 20-40 nm, H3 is 60-80 nm, and H3 is 120 nm.
The foregoing detailed description is intended to illustrate and not limit the invention, which is intended to be within the spirit and scope of the appended claims, and any changes and modifications that fall within the true spirit and scope of the invention are intended to be covered by the following claims.